MELSEC-F series Variety of functions
PLC standard counters can count at some 10 Hz maximum, but using FX PLC built-in high speed counters, high speed pulse inputs can be counted.
Built-in high speed counter numbers and allocation
Built-in high speed counters use general inputs X000 to X007. Input method and input terminal numbers are determined based on whether the counter uses 1-phase or 2-phase, and start or reset functions.
FX3S, FX3G, FX3GC, FX3U, FX3UC Series PLC
U: Up-counting input D: Down-counting input A: A phase input B: B phase input R: External reset input S: External start input
| Input number |
1-phase 1-count input | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| C235 | C236 | C237 | C238 | C239 | C240 | C241 | C242 | C243 | C244 | C244*1 (OP) |
C245 | C245*1 (OP) |
|
| X000 | U/D | U/D | U/D | ||||||||||
| X001 | U/D | R | R | ||||||||||
| X002 | U/D | U/D | U/D | ||||||||||
| X003 | U/D | R | R | ||||||||||
| X004 | U/D | U/D | |||||||||||
| X005 | U/D | R | |||||||||||
| X006 | S | U/D | |||||||||||
| X007 | S | U/D | |||||||||||
| Input number |
1-phase 2-count input | 2-phase 2-count input | Input assignment for FX3U-4HSX-ADP*3 |
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| C246 | C247 | C248 | C248 (OP) |
C249 | C250 | C251 | C252 | C253 | C253 (OP) |
C254 | C254*2 (OP) |
C255 | 1st unit | 2nd unit | |
| X000 | U | U | U | A | A | A | ○ | - | |||||||
| X001 | D | D | D | B | B | B | ○ | - | |||||||
| X002 | R | R | R | R | ○ | - | |||||||||
| X003 | U | U | U | A | A | A | - | ○ | |||||||
| X004 | D | D | D | B | B | B | - | ○ | |||||||
| X005 | R | R | R | R | - | ○ | |||||||||
| X006 | S | S | A | ○ | - | ||||||||||
| X007 | S | B | S | - | ○ | ||||||||||
- *1Only FX3U/FX3UC PLCs
- *2Only FX3G/FX3GC PLCs
- *3Only FX3U PLCs
[Examples]
By using C238 (1-phase 1-count), X003 automatically becomes high-speed input terminal.
Also, by using C252 (2-phase 2-count), X000 automically becomes A phase input,
X001 becomes B phase input, and X002 becomes reset input.
Maximum frequency that the PLC can process
For the maximum frequency that can be counted, please refer to the "Counter number max. response frequency" in the previous tables. Furthermore, each PLC has an "overall frequency" processing limit.
For details, please refer to each product manual.
High speed comparison results can be obtained by a simple program and no calculation delay
- 1) High-Speed Compare SET, RESET/High-Speed Zone Compare*
- *High speed band comparison instruction is for FX3S, FX3G, FX3GC, FX3U, FX3UC PLCs only
- 2) High-speed counter interrupt function (only FX3U/FX3UC PLCs)
- 3) Compare With Data Table (only FX3U/FX3UC PLCs)
- 4) High-Speed Counter Move (only FX3U/FX3UC PLCs)
FX3U, FX3U PLC counter modes
2-phase 1 edge count counter can be used as a 4 edge count counter by combining a special auxiliary relay (M8388, M8198, M8199).
| Types of high-speed counters | Pulse input signal form | |
|---|---|---|
| 1-phase 1-count input |  |
|
| 1-phase 2-count input |  |
|
| 2-phase 2-count input | 1 edge count |  |
| 4 edge count |  |
|